Principles of Naval Architecture (Second Revision), Volume I - Stability and Strength

337 Pages·1988·31.92 MB·English

by  Lewis

Principles of
Naval Architecture
Second Revision
Volume I Stability and Strength
Edward V. Lewis, Editor
1988
Published by
The Society of Naval Architects and Marine Engineers
601 Pavonia Avenue
Jersey City, NJ
Copyright @ 1988 by The Society of Naval Architects and Marine Engineers.
It is understood and agreed that nothing expressed herein is intended or shall be construed to
give any person, firm, or corporation any right, remedy, or claim against SNAME or any of its
officers or members.
Library of Congress Catalog Card No. 8860829
ISBN NO. 0-939773-00-7
Printed in the United States of America
First Printing, April, 1988
ii
Introduction
A Word From the President
The original version of this book, Principles of Naval Architecture, was first published
by the Society in 1939. Editors H. E. Rossell and L. B. Chapman stated that the purpose
of the work was to “adequately cover the field of naval architecture in one text.” This
they did, in two volumes, serving the Society’s students and members more than adequately
for nearly 30 years.
The First Revision was published in 1967, with John P. Comstock serving both as
Chairman of the Control Committee and Editor. It consisted of one volume containing 11
chapters and an Appendix. Continuing changes in naval architecture, such as technical
practices, new criteria and regulations regarding damage stability and ship strength, new
knowledge about ocean waves and seakeeping, and the use of computers, prompted the
Society to undertake the Second Revision in 1978. President Robert T. Young appointed
John J. Nachtsheim as Chairman of the Control Committee, and Professor Edward V.
Lewis was named Editor. Serving on the Control Committee, charged with the important
tasks of choosing the authors and review of the chapters, were Thomas M. Buermann,
William A. Cleary, Richard B. Couch, Jerome L. Goldman, Jacques B. Hadler, Ronald K.
Kiss, Donald P. Roseman, Stanley G. Stiansen and Charles Zeien. This Second Revision
of Principles of Naval Architecture (PNA) is the result of this Committee’s work.
Even though the First Revision chapters on tonnage admeasurement, load line assign-
ment and launching were removed from PNA to the 1980 edition of Ship Design and
Construction, the remaining PNA chapters were so enlarged by new material that the
decision was made to expand the Second Revision into three volumes.
Only the authors and the editors can appreciate the time and difficulties involved in
writing, reviewing and editing this mass of knowledge into suitable form for publication.
The work of these people, who are esteemed in their respective fields, has been as selfless
as it is priceless to our Society and its membership. The Society is deeply indebted to the
authors and to the tireless reviewers of the Control Committee.
To quote the late Matthew G. Forrest, a Past President of the Society, “The Society
hopes that this First Revision of Principles of Naval Architecture will prove to be as
useful, both to students and to those engaged in the practice of the profession, as the
original edition proved to be.”
I could not say it any better regarding the Second Revision.
EDWARDJ. CAMPBELL
President, SNAME
...
111
Preface
The aim of this second revision (third edition) of the Society’s successful Principles of Naval
Architecture was to bring the subject matter up-to-date through revising or rewriting areas of
greatest recent technical advances, which meant that some chapters would require many more
changes than others. The basic objective of the book, however, remained unchanged to provide a
timely survey of the basic principles in the field of Naval Architecture for the use of both students
and active professionals, making clear that research and engineering are continuing in almost all
branches of the subject. References are to be included to available sources of additional details and
to ongoing work to be followed in the future.
The preparation of this third edition was simplified by an earlier decision to incorporate a number
of sections into the companion SNAME publication, Ship Design and Construction, which was
revised in 1980. The topics of Load Lines, Tonnage Admeasurement and Launching seemed to be
more appropriate for the latter book, and so Chapters V, VI, and XI became IV, V and XVII
respectively, in Ship Design and Construction. This left eight chapters, instead of 11, for the
revised Principles of Naval Architecture.
At the outset of work on the revision, the Control Committee decided that the increasing importance
of high-speed computers demanded that their use be discussed in the individual chapters instead of
in a separate Appendix as before. It was also decided that throughout the book more attention
should be given to the rapidly developing advanced marine vehicles.
In regard to units of measure, it was decided that the basic policy would be to use the International
System of Units (S.I.). Since this is a transition period, conventional US. (or “English”) units would
be given in parentheses throughout the book. This follows the practice adopted for the Society’s
companion volume, Ship Design and Construction. The US. Metric Conversion Act of 1975 (P.L.
94-168) declared a national policy of increasing the use of metric systems of measurement and
established the US. Metric Board to coordinate voluntary conversion to S I. The Maritime Admin-
istration, assisted by a SNAME Ad Hoc Task Group, developed a Metric Practice Guide to “help
obtain uniform metric practice in the marine industry,” and this guide was used here as a basic
reference. Following this guide, ship displacement in metric tons (1000 kg) represents mass rather
than weight. (In this book the familiar symbol, A, is reserved for the displacement mass). When
forces are considered, the corresponding unit is the kilo-Newton (kN), which applies, for example,
to resistance and to displacement weight (symbol W, where W = Ag) or to buoyancy forces. (See
Chapter I.) When conventional or English units are used, displacement weight is in the familiar long
ton unit (2240 lb), which numerically is 1.015 x metric ton. A conversion table also is included with
the symbols and abbreviations or Nomenclature at the end of this volume.
This first volume of the third edition of Principles of Naval Architecture, comprising Chapters
I through IV, covers almost the same subject matter as the first four chapters of the preceding
edition. Thus, it deals with the essentially static principles of naval architecture, leaving most dynamic
aspects to the remaining volumes. Chapter I deals with the graphical and numerical description of
hull forms and the calculations needed to deal with problems of flotation and stability that follow.
Chapter I1 considers stability in normal intact conditions, while Chapter I11 discusses flotation and
stability in damaged conditions. Finally, Chapter IV deals with principles of hull structural design,
first under static calm water conditions, and then introducing the effect of waves which also is
covered more fully in Volume 111, Chapter VII on Seakeeping.
These first four chapters were found to require less revision than those dealing, for example,
with maneuverability and motions in waves. The latter required more time than anticipated. Some
of the principal changes may be noted:
In Chapter I there is some rearrangement and change of emphasis. A few additions were made,
such as developable lines and a containership, as well as a conventional cargo ship, as examples.
(Continued)
V
PREFACE
In Chapter I1 more attention is given to stability curves and to criteria for acceptable stability
based on them.
In Chapter I11 more space is allotted to standards of flooding and damage stability, with emphasis
on new probability-based international regulations.
Finally, Chapter IV has been extensively rewritten to cover new probabilistic techniques for dealing
with loads and structural analysis methods concerned with ultimate strength. Several sections,
including 3.3, Calculation of section modulus, and 3.14, Stress concentrations, were reproduced
without change from the earlier edition.
February 1988 EDWARDV. LEWIS
Editor
vi
Table of Contents
Volume I
Pag..e. Page
Introduction . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . y Editor’s Preface. ........... . ... .. . .. ..... .. v
Foreword.. .. ._.. . . .. ... .. . .. ... .. .. .. ...... IV Acknowledgments .......................... viii
Chapter 1 SHIP GEOMETRY
NORMANA . HAMLINP, rofessor, Webb Institute of Naval Architecture
1. Ships’ Lines. ..... ........ .... . .. .. . .. . . 1 5. Hydrostatic Curves and Calculations 31
2. Displacement and Weight 6. Bonjean Curves .... .. . .. .. . .... ...... .. 44
Relationships . . . . . . . . . . . . . .. . .. . . . . . . 16 7. Wetted Surface ........................ 47
3. Coefficients of Form.. ....... .......... 18 8. Capacity ............................... 51
4. Integrating Rules and Methods. ...... 22
Chapter 2 INTACT STABILITY
LAWRENCLE. GOLDBERG,U niversity of Maryland
1. Elementary Principles ... .. .. ..... ..... 63 8. Drafts Trim and Displacement ........ 115
2. The Weight Estimate .................. 69 9. The Inclinin Experiment .. . . . . . . . . . . . 122
3. Metacentric Hei ht ....... . .... .. .. .. . . 71 10. Submerged fkpilibrium . . . . . . . . . . . . . . . 128
4. Curves of Stabihy . .. ... .... . .. ..... .. 78 11. The Trim Dive.. . . . . . . . .. . . . . . . . . . . . . . . 134
5. Effect of Free Liquids and Special 12. Methods of Improving Stability,
Cargoes ....... .. ... .... ... ....... .. .. 93 Drafts and List ..................... 135
6. Effect of Changes in Weight on 13. Stabilit when Grounded .............. 136
Stability. ............................. 102 14. Intact &ability of Unusual Ship
7. Evaluation of Stability ... .... .... . .. .. 106 Forms.. . . .. ............ . . . . .. ... .. ... 138
Chapter 3 SUBDIVISION AND DAMAGE STABILITY
GEORGE C. NICKUMP, resident, Nickum & Spaulding Associates
1. Introduction ............................ 111 5. Subdivision and Damage Stability
2. Fundamental Effects of Damage ...... 146 Calculation b Computer.. ...... ... . 176
3. Subdivision and Dama e 6. Definitions for %tegulations.. . . . . . . . . . . 178
Dama e Stability C8culations . . . . . . 149 7. Subdivision and Damage Stability
4. Manual tubdivision and Damage Criteria .. . ...... . ... . .. . .. . .... .. . ... 180
Stability Calculations.. . . . . . . . . . . . . .. 152 8. Alternate Equivalent Passenger
Vessel Regulations . .. . .. . . . . . . . . . . . . 194
Chapter 4 STRENGTH OF SHIPS
J. RANDOLPHPA ULLINGP, rofessor, University of California, Berkeley
1. Introduction ...... . ... .. .. .. . .. .. ... .. .. 205 5. Reliability of Structures ............... 290
2. Ship Structural Loads ........ .... ..... 208
3. Analysis of Hull Girder Nomenclature . . . . . . . . . . .. . .. . . . . . . . . . . . . . .. 301
Girder Stress and Deflection ........ 233 Index ....................................... 305
4. Load Carryin Capability and
. . . .
Structural berformance Criteria 275
vii
CHAPTER I
I
Ship Geometry
Norman A. Hamlin
Section 1
Ships’ lines
1.1 Delineation and Arrangement of lines Draw- on the profile, with the body plan’s centerplane midway
ing. The exterior form of a ship’s hull is a curved between the ends of the ship in profile view. Planes
surface defined by the lines drawing, or simply “the defining the body plan are known as body plan stations.
lines.” Precise and unambiguous means are needed to They are usually spaced equally apart, such that there
describe this surface, inasmuch as the ship’s form must are 10 spaces-or multiples thereof-in the length of
be configured to accommodate all internals, must meet the ship, but with a few extra stations at the ends of
constraints of buoyancy, stability, speed and power, the ship at one half or one quarter this spacing.
and seakeeping, and must be “buildable.” Hence, the Most ships are symmetrical about the centerplane,
lines consist of orthographic projections of the inter- and the lines drawing shows waterlines in the half-
sections of the hull form with three mutually perpen- breadth plan on only one side of the centerline. Asym-
dicular sets of planes, drawn to a suitable scale. metrical features on some ships, such as overhanging
Fig. 1 shows a lines drawing for a single-screw flight decks on aircraft carriers, must be depicted sep-
cargo-passenger ship. arately. Correspondingly, the body plan shows sections
The profile or sheer plan shows the hull form in- on one side of the centerline only-those in the fore-
tersected by the centerplane-a vertical plane on the body on the right hand side and those in the afterbody
ship’s centerline-and by buttock planes which are on the left. By convention in the U.S., the bow of the
parallel to it, spaced for convenient definition of the ship is shown to the right. With the arrangement of
vessel’s shape and identified by their distance off the the lines as shown in Fig. 1, the drawing represents
centerplane. The centerplane intersection shows the a case of first angle projection in descriptive geometry.
profile of the bow and stern. Below the profile is the The lines in Fig. 1 represent the molded surface of
half-breadth or waterlines plan, which shows the in- the ship, a surface formed by the outer edges of the
tersection of the hull form with planes parallel to the frames, or inside of the “skin,” in the case of steel,
horizontal baseplane, which is called the base line. All aluminum and wooden vessels. In the case of glass
such parallel planes are called waterline planes, or reinforced plastic vessels, the molded surface is the
waterplanes. It is convenient to space most water- outside of the hull. (The term molded surface undoubt-
planes equally by an integral number of meters (or edly arose from the use of wooden “molds” set up to
feet and inches), but a closer spacing is often used establish a surface in space to which frames could be
near the baseline where the shape of hull form changes formed when wooden vessels were being built).
rapidly. DWL represents the design waterline, near The shell plating of a steel or aluminum ship con-
which the fully loaded ship is intended to float. All stitutes the outer covering of the molded surface. The
waterlines are identified by their height above the base- shell plating is relatively thin and is formed of plates
line. that are usually of varying thickness, causing some
The body plan shows the shapes of sections deter- unevenness, although the molded surf ace is generally
mined by the intersection of the hull form with planes smooth and continuous.
perpendicular to the buttock and waterline planes. In The thickness of planking of a wooden boat is rel-
Fig. 1 this is shown above the profile, but it might atively larger than the shell thickness of a steel vessel,
otherwise be drawn to the right or left of the profile, and it is the usual practice to draw the lines of a
using a single extended molded baseline, depending wooden boat to represent the surface formed by the
upon the width and length of paper being used. Al- outside of the planking, since this gives the true ex-
ternatively, the body plan is sometimes superimposed ternal form. However, for construction purposes it is
2 PRINCIPLES OF NAVAL ARCHITECTURE
necessary to deal with the molded form, and therefore hydrodynamic purposes, length on the prevailing
it is not unusual to find the molded form of wooden waterline may be significant; alternatively, an “effec-
vessels delineated on a separate lines drawing. tive length’’ of the underwater body for resistance
In the sheer plan of Fig. 1, the base line, repre- considerations is sometimes required.
senting the bottom of the vessel, is parallel to the One useful method of determining the after end of
DWL, showing that the vessel is designed for an “even- effective length is to make use of a sectional area
keel” condition. Some vessels-especially tugs and curve, whose ordinates represent the underwater cross
fishing vessels-are often designed with the molded sectional area of the vessel up to the DWL at a series
keel line raked downward aft, giving more draft at the of stations along its length. (See Section 1.7.) The ef-
stern than the bow when floating at the DWL; such fective length is usually considered as the overall
vessels are said to have a designed drag to the keel. length of the sectional area curve. However, if the
1.2 Perpendiculars; length Between PerpendicG- curve has a concave ending, a straight line from the
Iars. A vertical line in the sheer plan of Fig. 1 is drawn midship-cross-sectional area can be drawn tangent to
at the intersection of the DWL, which is often the the curve, as shown in Fig. 3. The intersection of this
estimated summer load line (defined subsequently), straight line tangent with the baseline of the graph
and the forward side of the stem. This is known as may then be considered to represent the after end of
the forward perpendicular, abbreviated as FP. A the effective length. On many single-screw designs it
slight inconsistency is introduced by this definition of has been found that the point so determined is close
FP in that the forward side of the stem is generally to the location of the AP. Such an effective length
in a surface exterior to the molded form by the thick- ending might then be used in calculating hull form
ness of contiguous shell plating-or by the stem thick- coefficients, as discussed in Section 3. A similar defi-
ness itself if the stem is of rolled plate. nition for the forward end of effective length might
A corresponding vertical line is drawn at the stern, be adopted for ships with protruding bulbous bows
designated the after perpendicular or AP. When extending forward of the FP.
there is a rudder post the AP is located where the after It is important that in all calculations and measure-
side of the rudder post intersects the DWL. In Fig. 1 ments relating to length, the method of determining
the AP is drawn at the centerline of the rudder stock, the length used, and the location of its extremities be
which is the customary location for merchant ships clearly defined.
without a well defined sternpost or rudder post. In the 1.3 Midrhip Section; Parallel Middle Body. An im-
case of naval ships, it is customary to define the AP portant matter for any ship is the location and shape
at the after end of the vessel on the DWL. Such a of the midship cross section, generally designated by
a,
location is also sometimes chosen for merchant ves- the symbol which was originally used to indicate
sels-especially vessels with a submerged stern profile the fullest cross section of the vessel. In some of the
extending well abaft the rudder. Fig. 2 shows the var- early sailing ships this fullest section was forward of
ious locations of the AP here described. the midlength, and in some high-speed ships and sailing
An important characteristic of a ship is its length yachts, the fullest section under water is somewhat
between perpendiculars, sometimes abbreviated LBP abaft the midlength. In any case, the usual practice in
or Lpp. This represents the fore-and-aft distance be- modern commercial vessels of most types is to locate
a
tween the FP and AP, and is generally the same as halfway between the perpendiculars, while in naval
the length L defined in the American Bureau of Ship- ships it is usually midway between the ends of the
ping Rules for Building and Classing Steel Vessels DWL.
(Annual)’. However, in the Rules there is included the In many modern vessels, particularly cargo vessels,
proviso that L, for use in the Rules, is not to be less the form of cross section below the DWL amidships
than 96 percent and need not be greater than 97 per- extends without change for some distance forward and
cent of the length on the summer load line. The sum- aft, usually including the midship location. Such ves-
mer load line is the deepest waterline to which a sels are said to have parallel middle body. The ship in
merchant vessel may legally be loaded during the sum- Fig. 1 has no parallel middle body, but the form of
mer months in certain specified geographical zones. section under water changes but slightly for small
Methods for determining the summer load line are distances forward or abaft the fullest section, which
covered in the discussion of freeboard in Ship Design is located amidships.
and Construction (Taggart, 1980). 1.4 Body Plan Stations; Frame lines; Deck lines. In
When comparing different designs, a consistent order to simplify the calculation of underwater form
method of measuring ship lengths should be used. characteristics, it is customary to divide the LBP into
Overall length is invariably available from the vessel’s 10-or 20, or 40-intervals by the body plan planes.
plans and LBP is usually also recorded. However, for The locations of these planes are known as body plan
stations, or simply stations, and are indicated by
straight lines drawn in the profile and half-breadth
plans at right angles to the vessel’s baseline and cen-
* Complete references are listed at end of chapter. terline, respectively. The intersections of these planes
? I14 I" y -vI,
V
body plan
0
3
rn
-4
W<
--M
3
ha-
- LENGTH BETWEEN PERF€NDICGRS--- 1% 9on 508.5 H - m P
PROFILE OR SHEER PUN
&
ion
I
4 PRINCIPLES OF NAVAL ARCHITECTURE
Body plan station planes are not to be confused with
planes at which the vessel’s frames are located, al-
DWL though frames are normally located in planes normal
to the baseplane and longitudinal centerplane, which
are therefore parallel to body plan station planes.
Frames are normally spaced to suit the structure and
arrangement of internals and their location is not de-
pendent upon station plane locations. On some naval
ships, frame spacing is an integral number of feet or
AP AP one meter. Frame locations are usually chosen early
in the design of a ship, and it is customary to show
them on arrangement drawings and frequently also
on final lines drawings. Therefore, frame locations, and
their spacing, must be clearly stated. A body plan at
frame locations is frequently drawn to assist the ship
yard in fabricating the frames.
Frames are generally numbered with integer num-
I bers, either starting at the FP and increasing aft, or
AP
at the AP and increasing forward. The latter practice
Fig. 2 Alternotivc locotions of ofter perpendiculor
is customary in tankers. In some instances, particu-
larly naval ships, frames have been identified by the
distance of the frame plane in meters from the FP.
with the molded form appear in their true shape in the A frame plane establishes a molded line, or surface,
body plan. which will be coincident with the plane of either the
Body plan stations are customarily numbered from forward or after edge of the frame. The location of
the bow, with the FP designated as station 0. In Europe frames, either forward of or abaft the frame line,
and Japan, however, station 0 is often located at the should be clearly stated on relevant drawings.
AP, with station numbering from aft forward. For the The outline of the ship is completed in the sheer plan
ship shown in Fig. 1, station No. 10 represents the by showing the line of the main deck at the side of
stern extremity of the vessel for calculations relating the ship, and also at the longitudinal centerline plane
to the underwater body. It will be noted that additional whenever, as is usual, the deck surface is crowned or
stations are drawn midway between stations 0 and 1, cambered, i.e., curved in an athwartship direction with
and 9 and 10, and sometimes between 1 and 2, and 8 convex surface upwards, or sloped by straight lines to
and 9, as well. This is done to better define the vessel’s a low point at the deck edge. A ship’s deck is also
form near the ends where it may change rapidly for usually given longitudinal sheer; i.e., it is curved u p
small longitudinal distances. wards towards the ends, usually more at the bow than
Additional stations are often also shown forward of at the stern. In case the sheer line of the deck at side
the FP and abaft the AP. These may receive letter or curves downward at the ends, the ship is said to have
distance designations from the perpendiculars, or a reverse sheer.
continuation of the numbering system equivalent to Similarly, lines are shown for the forecastle, bridge,
that used in the remainder of the ship, as negative and poop decks when these are fitted; sometimes decks
numbers forward of the FP and numbers in excess of below the main deck are also shown. All such deck
10 (or 20, etc.) abaft the AP. lines generally designate the molded surface of the
Ly-
AFTERBODY ___ct)___ FOREBODY
-pd k--
RUN MIDPAORLAELBLOEDL Y ENTRANCE
10 5 0
Fig. 3 Geometry of sectional ore0 curve